1. Field of the Invention
This invention relates to tower joints and, more particularly, to apparatus for connecting a pair of I-shaped beams in an end-to-end relationship.
2. Description of the Prior Art
Steel lattice towers are commonly used for supporting tower cranes and as booms for cranes. The towers include several tower sections bolted together to provide the required length. The tower sections are formed of a plurality of chords or lengths of beams interconnected by a plurality of cross members or braces to provide strength against excessive bending of the tower. In some of the prior art towers, the chords of adjacent tower sections are fastened together in an end-to-end fashion by connecting bolts between terminal plates which are welded to the ends of the chords of the adjacent sections.
These bolts must be designed for large magnitude tension forces acting along the chords. This requires that the bolts be made of a high strength alloy, that the bolts be heat treated and that they meet very strict quality control standards. All of these requirements make the bolts very expensive to manufacture. Due to the critical nature of the joints, the bolts must be tightened to a predetermined accurate preload value. The tightening process requires the use of special tools, instructions and procedures, and requires a lot of time to join two tower sections together.
Some prior art towers use chords having a circular cross section and use special clamps for joining the ends of adjacent round chords. These prior art clamps cannot be used with the H-shaped or the I-shaped beam chords.